Facsimile machine and facsimile communication system

ABSTRACT

A facsimile communication system includes a calling and a called facsimile machine connected via a communication network. Each of the facsimile machines has a timer value representing a maximum allowable response time for a response signal relative to a signal transmitted to the counterpart facsimile machine. Using the timer value, each of the facsimile machines monitors whether the response signal is received from the counterpart facsimile machine within the timer value. If the response signal is not received within the timer value, retransmission of the transmitted signal is required. The called facsimile machine transmits all timer value change information for increasing the timer value to the calling facsimile machine. The calling facsimile machine selects the optimum timer value change information within the range of the timer value change information received from the called facsimile machine, and transmits the selected timer value change information to the called facsimile machine. The calling and called facsimile machines increase their timer values using the selected timer value change information. Accordingly, even if a communication delay is caused in the communication network, the retransmission of the transmitted signal can be avoided.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation of U.S. Non-Provisional PatentApplication No. 09/290,762 filed Apr. 13, 1999.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to a facsimile machine and afacsimile communication system for carrying out facsimile communicationvia a communication network, such as a packet communication network,which differs from a public telephone network.

BRIEF SUMMARY OF THE INVENTION

[0003] A communication procedure between facsimile machines connected tothe telephone network is regulated by the ITU-T (InternationalTelecommunication Union Telecommunication Standardization Sector)Recommendation T. 30. In this communication procedure, after a call isset, image data is transmitted and received between facsimile machineswhile given control signals are exchanged in order. For confirmingwhether the communication is normally executed, each of the facsimilemachines monitors whether a response signal is received from thecounterpart facsimile machine within a given time in response to acertain signal transmitted thereto. If no such a response signal isreceived within the given time, the foregoing certain signal isretransmitted to the counterpart facsimile machine. Then, if no such aresponse signal is received even after given number times repetition ofthe retransmission, the facsimile machine judges that a transmissionfailure has occurred, and forcibly stops or interrupts the communicationwith the counterpart facsimile machine.

[0004] In recent years, following the rapid spread of the Internet, acommunication procedure for realizing facsimile communication via theInternet has been proposed. Facsimile machines are connected to thetelephone network, while the telephone network is connected to thepacket communication network forming the Internet via gateways.

[0005] One of the facsimile machines is connected to one of the gatewaysvia the telephone network, while another facsimile machine is connectedto another gateway via the telephone network. The gateways are connectedto each other via the packet communication network.

[0006] Between the facsimile machine and the gateway connected theretovia the telephone network, communication is carried out pursuant to thecommunication procedure regulated by the ITU-T Recommendation T. 30. Onthe other hand, between the gateways connected via the packetcommunication network, communication is carried out pursuant to acommunication procedure regulated by the ITU-T Recommendation T. 38.

[0007] The conventional communication technique, however, has thefollowing problem to be solved.

[0008] Since the packet communication network deals with a large numberof communications at a given frequency band, if the traffic amountsincrease, it is possible that large communication delays are generatedlocally. Thus, it is possible that a significant communication delayoccurs between the gateways while facsimile communication is executed.If a communication delay occurs between the gateways, such acommunication delay is transferred, as it is, to the telephone networkconnecting between the facsimile machine and the gateway. According tothe communication procedure regulated by the ITU-T Recommendation T. 30,if a communication delay larger than a given value is generated, it isjudged that a communication failure has occurred so that facsimilecommunication is forcibly interrupted.

[0009]FIG. 19 is a sequence diagram showing an example wherein facsimilecommunication is interrupted due to a communication delay caused betweengateways.

[0010] In this example, when the line connection is established throughan exchange of various control signals after a call is made, image datais transmitted from a calling facsimile machine to a calling-sidegateway. The image data should then be transmitted from the calling-sidegateway to a called-side gateway and further transmitted from thecalled-side gateway to a called facsimile machine.

[0011] Following the transmission of the image data, the callingfacsimile machine transmits an EOP (End of Procedures) signal and thengoes into a standby state awaiting an MCF (Message Confirmation) signalto be sent from the called facsimile machine in response to the EOPsignal.

[0012] However, if a large communication delay is caused in the packetcommunication network connecting between the calling-side gateway andthe called-side gateway, the image data transmitted from thecalling-side gateway is received, but being largely delayed, at thecalled-side gateway. Thus, it is possible that the called facsimilemachine can not receive the image data within a lapse of a given timefrom the transmission of the image data by the calling facsimilemachine.

[0013] If that happens, the MCF signal from the called facsimile machinecan not be received at the calling facsimile machine within a lapse of,for example, three seconds from the transmission of the EOP signal asregulated by the communication procedure. In this case, the callingfacsimile machine retransmits the EOP signal twice at intervals of threeseconds.

[0014] If the MCF signal from the called facsimile machine is notreceived even after two-times retransmission of the EOP signal, thecalling facsimile machine judges that a communication failure hasoccurred, and transmits a DCN (Disconnect) signal for forciblyinterrupting the communication.

[0015] Since the communication is forcibly interrupted due to anoccurrence of the foregoing communication delay, the communication cannot be rendered smooth and reliable.

SUMMARY OF THE INVENTION

[0016] Therefore, it is an object of the present invention to provide afacsimile machine and a facsimile communication system which can achievesmooth and reliable communication by reducing a possibility ofcommunication errors caused by a communication delay.

[0017] It is another object of the present invention to provide afacsimile machine and a facsimile communication system which can reducea possibility of communication errors caused by a communication delaybetween gateways.

[0018] According to one aspect of the present invention, there isprovided a facsimile machine comprising a timing monitor section havinga timer for setting a timer value representing a maximum allowableresponse time for a response signal to be received from a counterpartfacsimile machine, the timing monitor section monitoring whether theresponse signal is received from the counterpart facsimile machinewithin the timer value; a timer value change information transmittingsection which transmits first timer value change information, possessedby the subject facsimile machine, to the counterpart facsimile machine;a timer value change information detecting section which detects secondtimer value change information transmitted from the counterpartfacsimile machine, the second timer value change information selectedfrom the first timer value change information at the counterpartfacsimile machine; and a timer value changing section which changes thetimer value using the second timer value change information.

[0019] According to another aspect of the present invention, there isprovided a facsimile machine comprising a timing monitor section havinga timer for setting a timer value representing a maximum allowableresponse time for a response signal to be received from a counterpartfacsimile machine, the timing monitor section monitoring whether theresponse signal is received from the counterpart facsimile machinewithin the timer value; a timer value change information detectingsection which detects timer value change information transmitted fromthe counterpart facsimile machine, the timer value change informationpossessed by the counterpart facsimile machine; a timer value changeinformation selecting section which selects, from the timer value changeinformation detected at the timer value change information detectingsection, optimum timer value change information to be used in facsimilecommunication to follow, the optimum timer value change informationcommonly possessed by the subject facsimile machine; a timer valuechange information transmitting section which transmits the optimumtimer value change information to the counterpart facsimile machine; anda timer value changing section which changes the timer value using theoptimum timer value change information.

[0020] It may be arranged that the facsimile machine further comprises acommunication mode selecting section which selects, upon calling, acommunication mode for implementing facsimile communication with thecounterpart facsimile machine via a communication network other than atelephone network, wherein the timer value change information detectingsection detects the timer value change information only when thecommunication mode is selected at the communication mode selectingsection.

[0021] It may be arranged that the facsimile machine further comprises adial number storage section which stores dial numbers of counterpartfacsimile machines to which facsimile communication is to be implementedvia the communication network; and a dial number search section which,when a dial number is inputted, searches the dial number storage sectionfor the inputted dial number, wherein the communication mode selectingsection selects the communication mode when the inputted dial number islocated in the dial number storage section.

[0022] It may be arranged that the dial number storage section furtherstores optimum timer value change information for each of thecounterpart facsimile machines such that the dial number and thecorresponding optimum timer value change information are mutuallyretrievable from each other, and that, when the inputted dial number islocated in the dial number storage section by the dial number searchsection, the timer value change information selecting section selectsthe stored timer value change information corresponding to the locateddial number.

[0023] According to another aspect of the present invention, there isprovided a facsimile communication system comprising a calling facsimilemachine; a calling-side gateway connected to the calling facsimilemachine via a telephone network; a called-side gateway connected to thecalling-side gateway via a communication network other than thetelephone network; and a called facsimile machine connected to thecalled-side gateway via the telephone network, wherein the calledfacsimile machine comprises a timer for setting a first timer valuerepresenting a maximum allowable response time for a response signal tobe received from the calling facsimile machine; a called-side timervalue change information transmitting section which transmits firsttimer value change information, possessed by the called facsimilemachine, to the called-side gateway; a called-side timer value changeinformation detecting section which detects second timer value changeinformation transmitted from the called-side gateway, the second timervalue change information selected from the first timer value changeinformation at the called-side gateway; and a called-side timer valuechanging section which changes the first timer value using the secondtimer value change information, wherein the calling-side gatewaycomprises a called/calling communication delay estimating section whichestimates a delay time of a signal transmitted from the called-sidegateway to the calling-side gateway; a first calling-side timer valuechange information detecting section which detects the first timer valuechange information received from the called-side gateway; a firstcalling-side timer value change information selecting section which,based on the delay time, selects from the first timer value changeinformation first optimum timer value change information to be used infacsimile communication to follow; and a timer value change informationreplacing section which replaces the first timer value changeinformation with the first optimum timer value change information so asto transmit the first optimum timer value change information to thecalling facsimile machine, and wherein the calling facsimile machinecomprises a timer for setting a second timer value representing amaximum allowable response time for a response signal to be receivedfrom the called facsimile machine; a second calling-side timer valuechange information detecting section which detects the first optimumtimer value change information received from the calling-side gateway; asecond calling-side timer value change information selecting sectionwhich selects from the first optimum timer value change informationsecond optimum timer value change information to be used in facsimilecommunication to follow, the second optimum timer value changeinformation commonly possessed by the calling facsimile machine; acalling-side timer value change information transmitting section whichtransmits the second optimum timer value change information to thecalling-side gateway; and a calling-side timer value changing sectionwhich changes the second timer value using the second optimum timervalue change information.

[0024] According to another aspect of the present invention, there isprovided a facsimile communication system comprising a calling facsimilemachine; a calling-side gateway connected to the calling facsimilemachine via a telephone network; a called-side gateway connected to thecalling-side gateway via a communication network other than thetelephone network; and a called facsimile machine connected to thecalled-side gateway via the telephone network, wherein the calledfacsimile machine comprises a timer for setting a first timer valuerepresenting a maximum allowable response time for a response signal tobe received from the calling facsimile machine; a called-side timervalue change information transmitting section which transmits firsttimer value change information, possessed by the called facsimilemachine, to the called-side gateway; a first called-side timer valuechange information detecting section which detects second timer valuechange information transmitted from the called-side gateway, the secondtimer value change information selected from the first timer valuechange information at the called-side gateway; and a called-side timervalue changing section which changes the first timer value using thesecond timer value change information, wherein the calling facsimilemachine comprises a timer for setting a second timer value representinga maximum allowable response time for a response signal to be receivedfrom the called facsimile machine; a calling-side timer value changeinformation detecting section which detects third timer value changeinformation selected from the first timer value change information andreceived from the calling-side gateway; a calling-side timer valuechange information selecting section which selects from the third timervalue change information first optimum timer value change information tobe used in facsimile communication to follow, the first optimum timervalue change information commonly possessed by the calling facsimilemachine; a calling-side timer value change information transmittingsection which transmits the first optimum timer value change informationto the calling-side gateway; and a calling-side timer value changingsection which changes the second timer value using the first optimumtimer value change information, and wherein the called-side gatewaycomprises a calling/called communication delay estimating section whichestimates a delay time of a signal transmitted from the calling-sidegateway to the called-side gateway; a second called-side timer valuechange information detecting section which detects the first timer valuechange information received from the called facsimile machine; acalled-side timer value change information selecting section which,based on the delay time, selects from the first timer value changeinformation second optimum timer value change information to be used infacsimile communication to follow, the second optimum timer value changeinformation selected as the second timer value change information; and atimer value change information replacing section which replaces thefirst optimum timer value change information received from thecalling-side gateway with the second optimum timer value changeinformation so as to transmit the second optimum timer value changeinformation to the called facsimile machine.

[0025] According to another aspect of the present invention, there isprovided a facsimile communication system comprising a facsimile machineconnected to a telephone network; and a gateway connected to thetelephone network and another communication network other than thetelephone network, wherein the facsimile machine comprises a first timerfor setting a first timer value representing a maximum allowableresponse time for a response signal to be received from a counterpartfacsimile machine via the communication network and the gateway relativeto a signal transmitted to the counterpart facsimile machine via thegateway and the communication network; and a first flow control sectionwhich re-sets the first timer to the first timer value when a re-settingcommand signal is received from the gateway, the re-setting commandsignal commanding the first flow control section to re-set the firsttimer to the first timer value, the first flow control sectiontransmitting to the gateway a resetting response signal notifying thatre-setting of the first timer to the first timer value is finished, andwherein the gateway comprises a second timer for setting a second timervalue corresponding to the first timer value, the second timer valuerepresenting a maximum allowable response time for the response signalto be received from the counterpart facsimile machine via thecommunication network relative to the transmitted signal; and a secondflow control section which transmits the re-setting command signal tothe facsimile machine when the response signal is not received withinthe second timer value, the second flow control section re-setting thesecond timer to the second timer value when the re-setting responsesignal is received from the facsimile machine, the second flow controlsection repeating transmission of the re-setting command signal andre-setting of the second timer to the second timer value until theresponse signal is received within the second timer value.

[0026] It may be arranged that the second timer value is set to besmaller than the first timer value.

[0027] According to another aspect of the present invention, there isprovided a facsimile machine comprising a timing monitor sectionconnected to a communication line and having a timer for variablysetting a timer value for a response signal relative to a signaltransmitted via the communication line, the timing monitor sectionmonitoring whether the response signal is received within the timervalue set in the timer; a timer value change information transmittingsection which transmits timer value information via the communicationline; a timer value change information detecting section which detectstimer value information from a received signal via the communicationline; and a timer value changing section which changes the timer valueof the timer based on the timer value information detected at the timervalue change information detecting section.

[0028] According to another aspect of the present invention, there isprovided a facsimile communication system including a calling facsimilemachine and a called facsimile machine connected to said callingfacsimile via a communication line, wherein said calling facsimilemachine comprises: a timing monitor section having a timer for setting atimer value representing a maximum allowable response time for aresponse signal to be received from said called facsimile machine, saidtiming monitor section monitoring whether said response signal isreceived from said called facsimile machine within said timer value; atimer value change information transmitting section which transmitsfirst timer value change information, possessed by the subject facsimilemachine, to said called facsimile machine; a timer value changeinformation detecting section which detects second timer value changeinformation transmitted from said called facsimile machine, said secondtimer value change information selected from said first timer valuechange information at said called facsimile machine; and a timer valuechanging section which changes said timer value using said second timervalue change information; and wherein said called facsimile machinecomprises: a timing monitor section having a timer for setting a timervalue representing a maximum allowable response time for a responsesignal to be received from said calling facsimile machine, said timingmonitor section monitoring whether said response signal is received fromsaid calling facsimile machine within said timer value; a timer valuechange information detecting section which detects timer value changeinformation transmitted from said calling facsimile machine, said timervalue change information possessed by said calling facsimile machine; atimer value change information selecting section which selects, fromsaid timer value change information detected at said timer value changeinformation detecting section, optimum timer value change information tobe used in facsimile communication to follow, said optimum timer valuechange information commonly possessed by the subject facsimile machine;a timer value change information transmitting section which transmitssaid optimum timer value change information to said calling facsimilemachine; and a timer value changing section which changes said timervalue using said optimum timer value change information.

[0029] It may be arranged that the at least a pair of facsimile machinesare directly connected to a packet communication network.

[0030] It may be arranged that the timer value change informationtransmitting section, when working as the called facsimile machine,notifies the calling facsimile machine that the called facsimile machineis directly connected to the packet communication network and can beoperated based on a timer value designated by the calling facsimilemachine, and that the timer value change information transmittingsection, when working as the calling facsimile machine, transmits amaximum timer value for one communication to the called facsimilemachine so that an allowable communication time for one communicationbetween the calling and called facsimile machines is regulated by themaximum timer value.

[0031] It may be arranged that the maximum timer value is selected basedon an estimated communication delay in the packet communication networkand an image data amount to be transmitted.

[0032] It will be appreciated by those skilled in the art that changescould be made to the embodiments described above without departing fromthe broad inventive concept thereof. It is understood, therefore, thatthis invention is not limited to the particular embodiments disclosed,but it is intended to cover modifications within the spirit and scope ofthe present invention as defined by the appended claims.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0033] The present invention will be understood more fully from thedetailed description given hereinbelow, taken in conjunction with theaccompanying drawings.

[0034] In the drawings:

[0035]FIG. 1 is a functional block diagram showing the main functions ofa facsimile machine, when working as a called facsimile machine(receiver), according to a first preferred embodiment of the presentinvention;

[0036]FIG. 2 is a functional block diagram showing the main functions ofa facsimile machine, when working as a calling facsimile machine(transmitter), according to the first preferred embodiment of thepresent invention;

[0037]FIG. 3 is a diagram showing a structure of a facsimilecommunication system according to the first preferred embodiment of thepresent invention;

[0038]FIG. 4 is a block diagram showing a hardware structure of afacsimile machine according to the first preferred embodiment of thepresent invention;

[0039]FIG. 5 is a block diagram showing a hardware structure of agateway according to the first preferred embodiment of the presentinvention;

[0040]FIG. 6 is a sequence diagram for explaining a facsimilecommunication procedure between a calling and a called facsimilemachine;

[0041]FIG. 7 is a diagram showing a facsimile communication operationsequence according to the first preferred embodiment of the presentinvention;

[0042]FIG. 8 is a diagram showing a structure of a facsimilecommunication system according to a second preferred embodiment of thepresent invention;

[0043]FIG. 9 is a functional block diagram showing the main functions ofa gateway, when working as a calling-side gateway, according to thesecond preferred embodiment of the present invention;

[0044]FIG. 10 is a functional block diagram showing the main functionsof a gateway, when working as a called-side gateway, according to thesecond preferred embodiment of the present invention;

[0045]FIG. 11 is a diagram showing a facsimile communication operationsequence according to the second preferred embodiment of the presentinvention;

[0046]FIG. 12 is a diagram showing a structure of a facsimilecommunication system according to a third preferred embodiment of thepresent invention;

[0047]FIG. 13 is a functional block diagram showing the main functionsof a facsimile machine according to the third preferred embodiment ofthe present invention;

[0048]FIG. 14 is a functional block diagram showing the main functionsof a gateway according to the third preferred embodiment of the presentinvention;

[0049]FIG. 15 is a diagram showing a facsimile communication operationsequence according to the third preferred embodiment of the presentinvention;

[0050]FIG. 16 is a diagram showing a structure of a facsimilecommunication system according to a fourth preferred embodiment of thepresent invention;

[0051]FIG. 17 is a block diagram showing a hardware structure of afacsimile machine according to the fourth preferred embodiment of thepresent invention;

[0052]FIG. 18 is a diagram showing a facsimile communication operationsequence according to the fourth preferred embodiment of the presentinvention; and

[0053]FIG. 19 is a sequence diagram showing an example wherein facsimilecommunication is interrupted due to a communication delay caused betweengateways.

DETAILED DESCRIPTION OF THE INVENTION

[0054] Now, the preferred embodiments of the present invention will bedescribed hereinbelow with reference to the accompanying drawings.

[0055] <First Embodiment>

[0056]FIGS. 1 and 2 are functional block diagrams showing the mainfunctions of a facsimile machine, when working as a called facsimilemachine and a calling facsimile machine, respectively, according to thefirst preferred embodiment of the present invention. FIG. 3 is a diagramshowing a structure of a facsimile communication system according to thefirst preferred embodiment. FIG. 4 is a block diagram showing a hardwarestructure of the facsimile machine according to the first preferredembodiment. FIG. 5 is a block diagram showing a hardware structure of agateway according to the first preferred embodiment. FIG. 6 is asequence diagram for explaining a facsimile communication procedurebetween a calling and a called facsimile machine.

[0057] As shown in FIG. 3, a facsimile machine 111 is connected to agateway 211 via a telephone line 310. The gateway 211 is connected to apacket communication network 400. On the other hand, a facsimile machine121 is connected to a gateway 221 via a telephone line 320. The gateway221 is connected to the packet communication network 400. The packetcommunication network 400 is constituted by the Internet, for example.

[0058] Facsimile communication between the facsimile machine 111 and thefacsimile machine 121 is carried out via the packet communicationnetwork 400.

[0059] Between the facsimile machine 111 and the gateway 211 and betweenthe facsimile machine 121 and the gateway 221, facsimile communicationis carried out pursuant to the communication procedure regulated by theITU-T Recommendation T. 30. On the other hand, between the gateway 211and the gateway 221, facsimile communication is carried out pursuant tothe communication procedure regulated by the ITU-T Recommendation T. 38.

[0060] The facsimile machines 111 and 121 have mutually the samestructure, and the gateways 211 and 221 also have mutually the samestructure. Accordingly, the facsimile machine 111 and the gateway 211will be described hereinbelow.

[0061]FIG. 4 is a block diagram showing a hardware structure of thefacsimile machine 111 shown in FIG. 3.

[0062] In FIG. 4, a CPU 12 controls the whole of the machine and thushas a function of wholly dealing with a control of the flow of imagedata, a communication control, a network control and so on. The CPU 12is connected via a bus 11 to a ROM 13, a RAM 14, a modem NCU interface15, an image compressing restoring section 21, a line memory 22, animage processing section 23 and a device interface 26.

[0063] The ROM 13 stores control programs to be executed by the CPU 12and control data to be used in the execution of the control programs.Specifically, the ROM 13 stores a control program and control data forcarrying out the facsimile communication procedure. The ROM 13 furtherstores a later-described timer value change control program for changingtimer values regulated by the ITU-T Recommendation T. 30. The timervalues are each used for monitoring whether a signal from a counterpartfacsimile machine is received within a given response time, so as toconfirm whether facsimile communication is executed normally or not. TheROM 13 further stores a program for selecting a communication mode.Accordingly, in FIG. 4, the ROM 13 is shown as having a communicationmode selecting section 13 a.

[0064] The RAM 14 temporarily stores image data which is to betransmitted to or has been received from a counterpart facsimilemachine, and thus has a function of a transmission-reception buffer forimage data.

[0065] To the modem NCU interface 15 are connected a modem 16 and an NCU(Network Control Unit) 17. The modem 16 modulates a transmitting signaland demodulates a received signal so as to support functions pursuant tothe ITU-T Recommendation V. 17, the ITU-T Recommendation V. 34 and thelike. The NCU 17 is connected to the telephone line 310 and controlsconnection and disconnection relative to a counterpart facsimilemachine.

[0066] The image compressing restoring section 21 compresses image datato be transmitted based on MH (Modified Huffman) coding, MR (ModifiedREAD) coding, MMR (Modified Modified READ) coding or the like, whiledecompresses received compressed image data to restore the originalimage data. The line memory 22 temporarily stores image data which is tobe transmitted to or has been received from a counterpart facsimilemachine.

[0067] To the image processing section 23 are connected a printer 24 anda scanner 25. The image processing section 23 performs given imageprocessing on image data to be outputted to the printer 24 or image datainputted from the scanner 25.

[0068] To the device interface 26 are connected a mechanism controlsection 27 and an operation display section 28. The mechanism controlsection 27 comprises drivers for operating corresponding components ofthe machine, and sensors. The operation display section 28 is used forinputting operation data and setting data and for displaying suchinputted data and information about the state of the machine. Theoperation display section 28 includes operation keys for dialing anddoing others, a liquid-crystal panel, LED's (Light Emitting Diodes) andso on.

[0069] When transmitting image data, a user first sets an original sheetS and carries out a required operation for transmission using theoperation display section 28. Then, the scanner 25 reads an image of theoriginal sheet S and converts it into image data. The image data is thensubjected to the given image processing at the image processing section23 and once stored in the line memory 22. Subsequently, the image datais read out from the line memory 22 and compressed at the imagecompressing restoring section 21, and then stored in the RAM 14, workingas a transmission buffer, via the bus 11. Subsequently, the image datais read out from the RAM 14 and transferred to the modem NCU interface15 via the bus 11. Subsequently, the image data is transferred to themodem 16 where it is modulated, and then sent out onto the telephoneline 310 via the NCU 17.

[0070] On the other hand, when image data is received at the NCU 17 fromthe telephone line 310, the received image data is demodulated at themodem 16. Then, the image data is outputted onto the bus 11 via themodem NCU interface 15 and stored in the RAM 14 working as a receptionbuffer. Subsequently, the image data is read out from the RAM 14 andtransferred to the image compressing restoring section 21 via the bus11. The image data is decompressed so as to be restored as the originalimage data at the image compressing restoring section 21, and thentransferred to the image processing section 23 via the line memory 22.Subsequently, the image data is subjected to the given image processingat the image processing section 23 and then transferred to the printer24. In the printer 24, the image is printed on a paper sheet P based onthe transferred image data.

[0071] Communication between the facsimile machines 111 and 121 isimplemented based on control signals exchanged therebetween beforetransmission of image data. A control signal is read out from the ROM 13by the CPU 12 and transferred to the modem NCU interface 15 via the bus11. Subsequently, the control signal is transferred to the modem 16where it is modulated, and then sent out onto the telephone line 310 viathe NCU 17.

[0072] On the other hand, when a control signal is received at the NCU17 from the telephone line 310, the control signal is outputted onto thebus 11 via the modem NCU interface 15 and transferred to the CPU 12. TheCPU 12 analyzes the control signal and implements a communicationprocedure according to the analyzed contents. Image data received afteran exchange of the control signals is demodulated at the modem 16.

[0073]FIG. 5 is a block diagram showing a hardware structure of thegateway 211 shown in FIG. 3.

[0074] In FIG. 5, a CPU 32 controls the whole of the gateway and thushas a function of wholly dealing with a control of the flow of imagedata, a communication control, a network control and so on. The CPU 32is connected via a bus 31 to a ROM 33, a RAM 34, a modem NCU interface35, an image compressing restoring section 41, a line memory 42 and aLAN interface 43.

[0075] The ROM 33 stores control programs to be executed by the CPU 32and control data to be used in the execution of the control programs,including control programs and control data for carrying out thefacsimile communication procedures. The RAM 34 temporarily stores imagedata which is to be transmitted or has been received, and thus has afunction of a transmission-reception buffer for image data.

[0076] To the modem NCU interface 35 are connected a modem 36 and an NCU(Network Control Unit) 37. The modem 36 modulates a transmitting signaland demodulates a received signal so as to support functions pursuant tothe ITU-T Recommendation V. 17, the ITU-T Recommendation V. 34 and thelike. The NCU 37 is connected to the telephone line 310 and controlsconnection and disconnection relative to an associated facsimilemachine.

[0077] For checking an error of image data received via the telephoneline 310 or the packet communication network 400, the image compressingrestoring section 41 decompresses the received image data to restore theoriginal image data. When image data compression modes of a calling anda called facsimile machine differ from each other, the image compressingrestoring section 41 restores the original image data from the receivedimage data and then compresses the restored image data according to theimage data compression mode of the called facsimile machine. The linememory 42 temporarily stores image data which is to be transmitted orhas been received.

[0078] To the LAN interface 43 is connected an LCU (Line Control Unit)44 which is connected to the packet communication network 400. The LANinterface 43 divides into packets a control signal or image datareceived via the telephone line 310 and reconstructs a control signal orimage data from packets received via the packet communication network400. The LCU 44 controls connection and disconnection relative to acounterpart gateway.

[0079] Image data received via the telephone line 310 is transmitted tothe packet communication network 400 in the following manner: When imagedata is received at the NCU 37 from the telephone line 310, the receivedimage data is demodulated at the modem 36. Then, the image data isoutputted onto the bus 31 via the modem NCU interface 35 and stored inthe RAM 34 working as a transmission-reception buffer.

[0080] Subsequently, the image data is read out from the RAM 34 andtransferred to the image compressing restoring section 41 via the bus31. The image data is decompressed so as to be restored as the originalimage data at the image compressing restoring section 41. The restoredimage data is used only for checking an error thereof.

[0081] If no error is found, the image data is read out from the RAM 34and transferred to the LAN interface 43. The image data is divided intopackets at the LAN interface 43 and transmitted to the packetcommunication network 400 via the LCU 44.

[0082] On the other hand, image data received via the packetcommunication network 400 is transmitted via the telephone line 310 inthe following manner: When packets are received at the LCU 44 from thepacket communication network 400, the received packets are reconstructedinto image data at the LAN interface 43. The reconstructed image data isstored in the RAM 34 working as a transmission-reception buffer.

[0083] Subsequently, the image data is read out from the RAM 34 anddecompressed so as to be restored as the original image data at theimage compressing restoring section 41. The restored image data is usedonly for checking an error thereof.

[0084] If no error is found, the image data is read out again from theRAM 34 and transferred to the modem NCU interface 35 via the bus 31. Thetransferred image data is modulated at the modem 36 and sent out ontothe telephone line 310 via the NCU 37.

[0085]FIG. 6 is a sequence diagram for explaining a facsimilecommunication procedure between a calling and a called facsimilemachine.

[0086] When a CNG (Calling Tone) signal is sent from the callingfacsimile machine, the called facsimile machine closes the line andtransmits a CED (Called Station Identification) signal, an NSF(Non-Standard Facilities) signal and a DIS (Digital IdentificationSignal) in order.

[0087] Then, the calling facsimile machine transmits a DCS (DigitalCommand Signal) or an NSS (Non-Standard Facilities Set-up) signal.

[0088] Subsequently, the calling facsimile machine transmits a TCF(Training Check) signal.

[0089] When the TCF signal is normally received, the called facsimilemachine transmits a CFR (Confirmation to Receive) signal.

[0090] In response to receipt of the CFR signal, i.e. after an exchangeof the given control signals, the calling facsimile machine startstransmission of image data. Following the termination of the image datatransmission, the calling facsimile machine transmits an EOP (End ofProcedure) signal.

[0091] In response to receipt of the EOP signal, the called facsimilemachine transmits an MCF (Message Confirmation) signal.

[0092] In response to receipt of the MCF signal, the calling facsimilemachine transmits a DCN (Disconnect) signal so that the line isdisconnected.

[0093] For confirming whether the facsimile communication is normallyimplemented, each of the facsimile machines monitors whether a givensignal is received from the counterpart facsimile machine within anormal response time.

[0094] For example, upon transmitting the TCF signal, the callingfacsimile machine sets a T4 timer value (3 seconds). Then, unless theCFR signal is received within 3 seconds from the called facsimilemachine, the calling facsimile machine judges that a transmissionfailure has occurred, and retransmits the DCS or NSS signal and then theTCF signal.

[0095] On the other hand, upon transmitting the CFR signal, the calledfacsimile machine sets a T2 timer value (6 seconds). Then, unless imagedata is received within 6 seconds from the calling facsimile machine,the called facsimile machine judges that a transmission failure hasoccurred, and forcibly interrupts the communication.

[0096] The foregoing timer values each represent the normal maximumresponse time and are regulated in the ITU-T Recommendation T. 30.

[0097] As described before, the ROM 13 of the facsimile machine 111stores the timer value change control program for changing the timervalues regulated in the ITU-T Recommendation T. 30 by mutual agreementwith a counterpart facsimile machine.

[0098] For achieving such an agreement, the NSF signal and the NSSsignal exchanged in the facsimile communication procedure are used. TheNSF signal includes all timer value change information possessed by thesubject facsimile machine (the machine which transmits the NSF signal).The NSS signal includes timer value change information to be used infacsimile communication to follow (to be implemented subsequently).

[0099] The timer value change information is, for example, informationfor increasing a timer value of the ITU-T Recommendation T. 30“twofold”.

[0100] The NSF signal is a signal for notifying a counterpart facsimilemachine of all non-standard communication capabilities possessed by thesubject facsimile machine (the machine which transmits the NSF signal).The NSS signal is a signal for selecting the optimum communicationcapability for use in facsimile communication to follow, fromcommunication capabilities possessed by the subject facsimile machine(the machine which transmits the NSS signal) within the range of thecommunication capabilities included in the NSF signal, so as to notifythe selected communication capability to a counterpart facsimilemachine.

[0101]FIGS. 1 and 2 show called-side and calling-side functional blocksrealized by executing the timer value change control program stored inthe ROM 13 of the facsimile machine, respectively.

[0102] Specifically, FIG. 1 shows the called-side functional blocks fortransmitting to a calling facsimile machine an NSF signal including alltimer value change information (communication capabilities) possessed bythe subject facsimile machine and receiving an NSS signal from thecalling facsimile machine. FIG. 2 shows the calling-side functionalblocks for receiving an NSF signal from a called facsimile machine andtransmitting to the called facsimile machine an NSS signal includingselected timer value change information (communication capability).

[0103] In FIG. 1, a timer value change information transmitting section51 transmits all timer value change information possessed by a calledfacsimile machine as an NSF signal. The timer value change informationtransmitting section 51 has a function of transmitting, for example,three kinds of timer value change information for increasing a timervalue “twofold”, “threefold” and “fourfold”, respectively. Hereinafter,these three kinds of timer value change information will be referred toas timer value change information of “twofold”, timer value changeinformation of “threefold” and timer value change information of“fourfold”, respectively.

[0104] A timer value change information detecting section 52 has afunction of detecting timer value change information included in an NSSsignal received from a calling facsimile machine. This timer valuechange information has been selected by the calling facsimile machine asthe optimum timer value change information for use in facsimilecommunication to follow, from timer value change information possessedby the calling facsimile machine within the range of the timer valuechange information of the given kinds transmitted by the foregoing timervalue change information transmitting section 51.

[0105] A timer value changing section 53 has a function of holding thetimer values of the ITU-T Recommendation T. 30. The timer value changingsection 53 has a further function of outputting to a timing monitorsection 54 the corresponding timer value of the ITU-T Recommendation T.30 as it is when the timer value change information is not detected atthe timer value change information detecting section 52. The timer valuechanging section 53 has a further function of, when the timer valuechange information is detected at the detecting section 52, changing thecorresponding timer value based on the detected timer value changeinformation and outputting the changed timer value to the timing monitorsection 54.

[0106] For example, when the timer value change information of “twofold”is detected at the timer value change information detecting section 52,the T2 timer value is changed to 12 seconds. In this case, the T4 timervalue is changed to 6 seconds in the calling facsimile machine.

[0107] The timing monitor section 54 has a function of monitoringwhether a response signal from the calling facsimile machine is receivedwithin a normal response time. Specifically, the timing monitor section54 holds the timer value outputted from the timer value changing section53 and sets it in a timer 55 at a given timing. Unless the responsesignal is received within a time represented by the timer value set inthe timer 55, the timing monitor section 54 outputs a time-out signalTOUT indicative of it.

[0108] In FIG. 2 showing the calling side, the RAM 14 has a dial numberstorage section 61. The dial number storage section 61 stores a dialnumber of each of counterpart facsimile machines to which facsimilecommunication is implemented via the packet communication network 400,and the optimum timer value change information for the correspondingcounterpart facsimile machine, such that the dial number and thecorresponding optimum timer value change information are mutuallyretrievable from each other.

[0109] A dial number search section 62 has a function of, when a dialnumber of a counterpart facsimile machine is inputted via the operationdisplay section 28 for making a call, searching the dial number storagesection 61 for the inputted dial number. The dial number search section62 has a further function of, when the inputted dial number is locatedin the dial number storage section 61, reading out timer value changeinformation stored corresponding to the located dial number andoutputting it to a timer value change information selecting section 64.

[0110] A timer value change information detecting section 63 has afunction of detecting timer value change information included in an NSFsignal received from a called facsimile machine. The NSF signal includesall timer value change information possessed by the called facsimilemachine.

[0111] The timer value change information selecting section 64 has afunction of selecting the optimum timer value change information for usein facsimile communication to follow, from timer value changeinformation possessed by the subject facsimile machine within the rangeof the timer value change information detected at the timer value changeinformation detecting section 63. The selecting section 64 has a furtherfunction of, when the timer value change information is inputted fromthe dial number search section 62, selecting the inputted timer valuechange information as the optimum timer value change information. Theselecting section 64 has a further function of outputting the selectedtimer value change information to a timer value changing section 53 anda timer value change information transmitting section 65.

[0112] The timer value change information transmitting section 65 has afunction of transmitting the timer value change information selected atthe timer value change information selecting section 64 as an NSSsignal.

[0113]FIG. 7 is a diagram showing a facsimile communication operationsequence according to the first preferred embodiment of the presentinvention.

[0114] It is assumed that the facsimile machine 111 is a callingfacsimile machine working as a transmitter for transmitting image data,while the facsimile machine 121 is a called facsimile machine working asa receiver for receiving image data.

[0115] First, the facsimile machine 111 is inputted with a dial numberof the facsimile machine 121 for making a call thereto. Then, the dialnumber search section 62 searches the dial number storage section 61 tolocate the inputted dial number, and outputs timer value changeinformation of, for example, “twofold” corresponding to the located dialnumber to the timer value change information selecting section 64. Inresponse to this output, the communication mode selecting section 13 aof the facsimile machine 111 selects a communication mode forimplementing facsimile communication via the packet communicationnetwork 400. Then, a call is made to the gateway 211 (step S1).

[0116] In response to the call from the facsimile machine 111 to thegateway 211, the line is established therebetween. Then, a dial tone DTis transmitted from the gateway 211 to the facsimile machine 111 (stepS2). In response to receipt of the dial tone DT from the gateway 211,the facsimile machine 111 transmits the dial number (PB signal) of thefacsimile machine 121 to the gateway 211 (step S3).

[0117] In response to receipt of the PB signal, the gateway 211retrieves an IP address of the gateway 221 in the packet communicationnetwork 400 from addresses stored in the RAM 34, and transmits to thegateway 221 a connection request adding the dial number of the facsimilemachine 121 (step S4).

[0118] In response to receipt of the connection request from the gateway211, the gateway 221 makes a call to the facsimile machine 121 (stepS5).

[0119] In response to the call from the gateway 221 to the facsimilemachine 121, the line is established therebetween. Then, the facsimilemachine 121 transmits to the gateway 221 a CED signal, an NSF signal anda DIS in order. The NSF signal transmitted from the timer value changeinformation transmitting section 51 of the facsimile machine 121includes three kinds of timer value change information of “twofold”,“threefold” and “fourfold” which are possessed by the facsimile machine121 (step S6).

[0120] The gateway 221 divides the NSF signal and the DIS received fromthe facsimile machine 121 into packets and transmits the packets to thegateway 211 (step S7).

[0121] The gateway 211 reconstructs the NSF signal and the DIS from thereceived packets and transmits them to the facsimile machine 111 (stepS8).

[0122] When the NSF signal and the DIS are received at the facsimilemachine 111, the timer value change information detecting section 63detects the foregoing timer value change information included in the NSFsignal. Specifically, the timer value change information of “twofold”,the timer value change information of “threefold” and the timer valuechange information of “fourfold” are detected. Then, the timer valuechange information selecting section 64 selects the timer value changeinformation of “twofold” according to the output from the dial numbersearch section 62. In response to this selection, the timer valuechanging section 53 increases the timer value twofold. Simultaneously,the timer value change information transmitting section 65 transmits thetimer value change information of “twofold” to the gateway 211 as an NSSsignal (step S9).

[0123] Subsequently, the facsimile machine 111 transmits a TCF signal tothe gateway 211. Simultaneously, at the timing monitor section 54 of thefacsimile machine 111, a twofold-increased T4 timer value (6 seconds) isset in the timer 55 (step S10).

[0124] The gateway 211 divides the NSS signal received from thefacsimile machine 111 into packets and transmits the packets to thegateway 221, and then goes into a standby state awaiting receipt of theTCF signal from the facsimile machine 111. When the gateway 211 normallyreceives the TCF signal from the facsimile machine, the gateway 211 goesinto a standby state awaiting receipt of a CFR signal from the gateway221 (step S12).

[0125] The gateway 221 reconstructs the NSS signal from the receivedpackets and transmits it to the facsimile machine 121 (step S12). Then,the gateway 221 produces a TCF signal according to a modem mode set bythe NSS signal and transmits it to the facsimile machine 121 (step S13).

[0126] When the NSS signal is received at the facsimile machine 121, thetimer value change information detecting section 52 thereof detects thetimer value change information of “twofold” included in the NSS signal.Then, the timer value changing section 53 increases the timer valuetwofold (step S14).

[0127] In response to receipt of the TCF signal, the facsimile machine121 transmits a CFR signal to the gateway 221. Simultaneously, at thetiming monitor section 54 of the facsimile machine 121, atwofold-increased T2 timer value (12 seconds) is set in the timer 55(step S15).

[0128] When the CFR signal is received from the facsimile machine 121,the gateway 221 divides the received CFR signal into packets andtransmits the packets to the gateway 211. At this time, if a largecommunication delay occurs in the packet communication network 400, thepackets (CFR signal) reach the gateway 211 with a corresponding delay(step S16).

[0129] The gateway 211 reconstructs the CFR signal from the packetsreceived from the gateway 221 and transmits the CFR signal to thefacsimile machine 111 (step S17).

[0130] The facsimile machine 111 receives the CFR signal from thegateway 211. If the normal T4 timer value (3 seconds) is set in thetimer 55 at step S10, since more than 3 seconds have elapsed after thetransmission of the TCF signal in an example of FIG. 7, it is necessarythat the facsimile machine 111 retransmits the NSS signal and the TCFsignal. However, in the example of FIG. 7, the twofold-increased T4timer value of 6 seconds is set at step S10 and further the CFR signalis received within a lapse of 6 seconds, although after a lapse of 3seconds, from the transmission of the TCF signal. Accordingly, thefacsimile machine 111 recognizes that the CFR signal is received withinthe normal response time. Thus, the retransmission of the NSS signal andthe TCF signal, which would be otherwise required due to the delay ofthe CFR signal relative to the TCF signal caused by the foregoingcommunication delay from the gateway 221 to the gateway 211, is notrequired so that the delay of the CFR signal relative to the TCF signalcan be absorbed.

[0131] In response to receipt of the CFR signal from the gateway 211,the facsimile machine 111 transmits image data to the gateway 211 (stepS18).

[0132] The gateway 211 divides the image data received from thefacsimile machine 111 into packets and transmits the packets to thegateway 221. At this time, if a large communication delay is caused inthe packet communication network 400, the packets (image data) reach thegateway 221 with a corresponding delay (step S19).

[0133] The gateway 221 reconstructs the image data from the packetsreceived from the gateway 211 and transmits the image data to thefacsimile machine 121 (step S20).

[0134] The facsimile machine 121 receives the image data from thegateway 221. If the normal T2 timer value (6 seconds) is set in thetimer 55 at step S15, since more than 6 seconds have elapsed after thetransmission of the CFR signal in the example of FIG. 7, the facsimilemachine 121 interrupts the reception process. However, in the example ofFIG. 7, the twofold-increased T2 timer value of 12 seconds is set atstep S15 and further the image data is received within a lapse of 12seconds, although after a lapse of 6 seconds, from the transmission ofthe CFR signal. Accordingly, the facsimile machine 121 recognizes thatthe image data is received within the normal response time. Thus, thedelay of the image data relative to the CFR signal caused by thecommunication delay from the gateway 211 to the gateway 221 can beabsorbed like the delay of the CFR signal relative to the TCF signal(step S21).

[0135] After the transmission of the image data, the facsimile machine111 transmits an EOP signal to the gateway 211. Simultaneously, thetiming monitor section 54 of the facsimile machine 111 sets atwofold-increased T4 timer value (6 seconds) in the timer 55 (step S22).

[0136] The gateway 211 divides the EOP signal received from thefacsimile machine 111 into packets and transmits the packets to thegateway 221. At this time, transmission of the packets (EOP signal) isdelayed following the transmission delay of the image data (step S23).

[0137] The gateway 221 reconstructs the EOP signal from the packetsreceived from the gateway 211 and transmits the EOP signal to thefacsimile machine 121 (step S24).

[0138] In response to receipt of the EOP signal from the gateway 221,the facsimile machine 121 transmits an MCF signal to the gateway 221(step S25).

[0139] The gateway 221 divides the received MCF signal into packets andtransmits the packets to the gateway 211 (step S26).

[0140] The gateway 211 reconstructs the MCF signal from the receivedpackets and transmits the MCF signal to the facsimile machine 111 (stepS27).

[0141] The facsimile machine 111 receives the MCF signal from thegateway 211. If the normal T4 timer value (3 seconds) is set in thetimer 55 at step S22, since more than 3 seconds have elapsed after thetransmission of the EOP signal in the example of FIG. 7, it is necessarythat the facsimile machine 111 retransmits the EOP signal. However, inthe example of FIG. 7, the twofold-increased T4 timer value of 6 secondsis set at step S22 and further the MCF signal is received within a lapseof 6 seconds, although after a lapse of 3 seconds, from the transmissionof the EOP signal. Accordingly, the facsimile machine 111 recognizesthat the MCF signal is received within the normal response time. Thus,the delay of the MCF signal relative to the EOP signal caused by thecommunication delay from the gateway 221 to the gateway 211 can beabsorbed like the delay of the CFR signal or the image data.

[0142] In response to receipt of the MCF signal, the facsimile machine111 transmits a DCN signal to the gateway 211 so that the line betweenthe facsimile machine 111 and the gateway 211 is disconnected (stepS28).

[0143] The DCN signal is transmitted to the facsimile machine 121 viathe gateways 211 and 221 to finally disconnect the line between thefacsimile machine 121 and the gateway 221, so that the communicationbetween the facsimile machines 111 and 121 is terminated (step S29).

[0144] As described above, according to the first preferred embodimentof the present invention, the timer value change informationtransmitting section 51 of the called facsimile machine 121 notifies alltimer value change information possessed by the subject facsimilemachine 121 to the calling facsimile machine 111 as the NSF signal.

[0145] Then, the timer value change information detecting section 63 ofthe facsimile machine 111 detects the timer value change informationincluded in the NSF signal. Subsequently, the timer value changeinformation selecting section 64 selects the optimum timer value changeinformation, also possessed by the subject facsimile machine 111, fromthe detected timer value change information. Then, the timer valuechanging section 53 of the facsimile machine 111 changes the timer valuebased on the selected timer value change information. On the other hand,the timer value change information transmitting section 65 notifies theselected timer value change information to the called facsimile machine121 as the NSS signal.

[0146] Then, the timer value change information detecting section 52 ofthe called facsimile machine 121 detects the timer value changeinformation included in the received NSS signal. Subsequently, the timervalue changing section 53 of the facsimile machine 121 changes the timervalue based on the detected timer value change information.

[0147] Thereafter, the facsimile machines 111 and 121 execute subsequentfacsimile communication using the commonly changed timer values,respectively.

[0148] Accordingly, the influence of a communication delay in the packetcommunication network 400 between the gateways 211 and 221 can beabsorbed between the facsimile machines 111 and 121. Therefore, apossibility of communication errors caused by such a communication delaycan be reduced to realize the highly reliable facsimile communication.

[0149] Further, the dial number storage section 61 stores a dial numberof each of counterpart facsimile machines to which facsimilecommunication is implemented via the packet communication network 400.When a dial number of a counterpart facsimile machine is inputted formaking a call, the dial number search section 62 searches the dialnumber storage section 61 for the inputted dial number.

[0150] Thus, it is possible to judge upon making a call whether tocommunicate via the packet communication network 400. Accordingly, itmay be arranged to detect the timer value change information from theNSF signal only when it is judged to communicate via the packetcommunication network 400.

[0151] It may be arranged that the operation display section 28 isprovided with an operation key for selecting a communication modeimplemented via the packet communication network 400. By using thisoperation key, the communication mode via the packet communicationnetwork 400 can be selected upon inputting a dial number. With thisarrangement, even if an inputted dial number is not stored in the dialnumber storage section 61, whether to communicate via the packetcommunication network 400 can be judged upon making a call.

[0152] Further, the dial number storage section 61 stores a dial numberof each of counterpart facsimile machines and the optimum timer valuechange information for the corresponding counterpart facsimile machine,such that the dial number and the corresponding optimum timer valuechange information are mutually retrievable from each other. With thisarrangement, when an inputted dial number is located in the dial numberstorage section 61 by the dial number search section 62, the timer valuechange information corresponding to the located dial number is directlyselected by the timer value change information selecting section 64 asthe optimum timer value change information.

[0153] Therefore, the optimum timer value change informationcorresponding to the counterpart facsimile machine can be selectedeasily and reliably.

[0154] <Second Embodiment>

[0155]FIG. 8 is a diagram showing a structure of a facsimilecommunication system according to the second preferred embodiment of thepresent invention.

[0156] As shown in FIG. 8, a facsimile machine 112 is connected to agateway 212 via a telephone line 310. The gateway 212 is connected to apacket communication network 400. On the other hand, a facsimile machine122 is connected to a gateway 222 via a telephone line 320. The gateway222 is connected to the packet communication network 400.

[0157] Facsimile communication between the facsimile machine 112 and thefacsimile machine 122 is carried out via the packet communicationnetwork 400.

[0158] The facsimile machines 112 and 122 have mutually the samestructure, and the gateways 212 and 222 also have mutually the samestructure. Accordingly, the facsimile machine 112 and the gateway 212will be described hereinbelow.

[0159] The facsimile machine 112 is the same in hardware structure asthe facsimile machine 111 shown in FIG. 4, but does not have either ofthe dial number storage section 61 and the dial number search section 62shown in FIG. 2.

[0160] The gateway 212 is the same in hardware structure as the gateway211 shown in FIG. 5, but a ROM 33 thereof stores a timer value changecontrol program for changing timer values of the facsimile machine 112connected thereto via the telephone line 310.

[0161]FIGS. 9 and 10 show calling-side and called-side functional blocksrealized by executing the timer value change control program stored inthe ROM 33, respectively.

[0162] Specifically, FIG. 9 shows the calling-side functional blocksproduced in a calling-side gateway which receives via a called-sidegateway an NSF signal transmitted from a called facsimile machine andwhich receives an NS S signal transmitted from a calling facsimilemachine. FIG. 10 shows the called-side functional blocks produced in acalled-side gateway which receives an NSF signal transmitted from acalled facsimile machine and which receives via a calling-side gatewayan NSS signal transmitted from a calling facsimile machine.

[0163] Assuming that the facsimile machine 122 is a called facsimilemachine and transmits an NSF signal and that the facsimile machine 112is a calling facsimile machine and transmits an NSS signal, the NSFsignal and the NSS signal are identified as follows:

[0164] An NSF 1-FG signal represents an NSF signal which is transmittedfrom the called facsimile machine 122 and received at the gateway 222.An NSF1-GG signal represents an NSF signal which is transmitted from thegateway 222 and received at the gateway 212. An NSF2-GF signalrepresents an NSF signal which is transmitted from the gateway 212 andreceived at the calling facsimile machine 112.

[0165] An NSS1-FG signal represents an NSS signal which is transmittedfrom the calling facsimile machine 112 and received at the gateway 212.An NSS1-GG signal represents an NSS signal which is transmitted from thegateway 212 and received at the gateway 222. An NSS2-GF signalrepresents an NSS signal which is transmitted from the gateway 222 andreceived at the called facsimile machine 122.

[0166] On the other hand, assuming that the facsimile machine 112 is acalled facsimile machine and transmits an NSF signal and that thefacsimile machine 122 is a calling facsimile machine and transmits anNSS signal, an NSF1-FG signal represents an NSF signal which istransmitted from the called facsimile machine 112 and received at thegateway 212, and similarly, the foregoing relationships with respect tothe other NSF and NSS signals are also reversed.

[0167] Referring to FIG. 9, when the calling-side gateway, for example,the gateway 212, sends a connection request to the called-side gateway222 to establish the line therebetween, a called/calling communicationdelay estimating section 71 of the calling-side gateway 212 estimates acommunication delay time of a signal transmitted from the called-sidegateway 222 to the calling-side gateway 212.

[0168] The delay time is estimated by utilizing a procedure regulated bythe ICMP (Internet Control Message Protocol), for example. Specifically,the delay time estimation is carried out by transmitting an echo requestmessage to the gateway 222 and measuring a time from transmission of theecho request message to receipt of an echo reply message transmittedfrom the gateway 222 in response thereto.

[0169] When an NSF1-GG signal (NSF1-FG signal of the called facsimilemachine 122) is received from the called-side gateway 222, a timer valuechange information detecting section 72 of the calling-side gateway 212detects timer value change information included in the received NSF1-GGsignal.

[0170] Based on the delay time estimated at the called/callingcommunication delay estimating section 71, a transmitter timer valuechange information selecting section 73 of the calling-side gateway 212selects the optimum timer value change information, with respect tosignal transmission from the called-side gateway 222 to the calling-sidegateway 212, from the timer value change information detected at thetimer value change information detecting section 72.

[0171] A transmitter timer value change information replacing section 74of the calling-side gateway 212 transmits the timer value changeinformation selected at the transmitter timer value change informationselecting section 73 to the calling facsimile machine 112 as an NSF2-GFsignal.

[0172] Specifically, the calling-side gateway 212 selects the optimumtimer value change information, with respect to signal transmission fromthe gateway 222 to the gateway 212, from the timer value changeinformation of the called facsimile machine 122 received via the gateway222, and transmits it to the calling facsimile machine 112. The optimumtimer value change information is selected based on an estimated valueabout a communication delay time of a signal transmitted from thegateway 222 to the gateway 212.

[0173] When an NSS1-FG signal is received from the calling facsimilemachine 112, the calling-side gateway 212 transmits the received NSS1-FGsignal as it is to the called-side gateway 222 as an NSS1-GG signal.

[0174] Referring to FIG. 10, when the called-side gateway, for example,the gateway 222, receives a connection request from the calling-sidegateway 212 to establish the line therebetween, a calling/calledcommunication delay estimating section 81 of the called-side gateway 222estimates a communication delay time of a signal transmitted from thecalling-side gateway 212 to the called-side gateway 222.

[0175] When an NSF1-FG signal is received from the called facsimilemachine 122, a timer value change information detecting section 82 ofthe called-side gateway 222 detects timer value change informationincluded in the received NSF1-FG signal.

[0176] Based on the delay time estimated at the calling/calledcommunication delay estimating section 81, a receiver timer value changeinformation selecting section 83 of the called-side gateway 222 selectsthe optimum timer value change information, with respect to signaltransmission from the calling-side gateway 212 to the called-sidegateway 222, from the timer value change information detected at thetimer value change information detecting section 82.

[0177] When an NSS1-GG signal (NSS1-FG signal of the calling facsimilemachine 112) is received from the calling-side gateway 212, a receivertimer value change information replacing section 84 of the called-sidegateway 222 replaces timer value change information included in thereceived NSS1-GG signal with the timer value change information selectedat the receiver timer value change information selecting section 83, andtransmits an NSS2-GF signal including the substituted timer value changeinformation to the called facsimile machine 122.

[0178] Specifically, the called-side gateway 222 selects the optimumtimer value change information from the timer value change informationof the called facsimile machine 122 and transmits it to the facsimilemachine 122. This optimum timer value change information is selectedbased on an estimated value about a communication delay time of a signaltransmitted from the gateway 212 to the gateway 222.

[0179] When the NSF1-FG signal is received from the called facsimilemachine 122, the gateway 222 transmits the received NSF1-FG signal as itis to the calling-side gateway 212 as an NSF1-GG signal.

[0180]FIG. 11 is a diagram showing a facsimile communication operationsequence according to the second preferred embodiment of the presentinvention.

[0181] It is assumed that the facsimile machine 112 is a callingfacsimile machine working as a transmitter for transmitting image data,while the facsimile machine 122 is a called facsimile machine working asa receiver for receiving image data.

[0182] First, the facsimile machine 112 makes a call to the gateway 212(step S101). In response to the call from the facsimile machine 112 tothe gateway 212, the line is established therebetween. Then, a dial toneDT is transmitted from the gateway 212 to the facsimile machine 112(step S102). In response to receipt of the dial tone DT from the gateway212, the facsimile machine 112 transmits a dial number (PB signal) ofthe facsimile machine 122 to the gateway 212 (step S103).

[0183] In response to receipt of the PB signal, the gateway 212retrieves an IP address of the gateway 222 in the packet communicationnetwork 400 from addresses stored in a RAM 34, and transmits to thegateway 222 a connection request adding the dial number of the facsimilemachine 122. At this time, the called/calling communication delayestimating section 71 of the calling-side gateway 212 estimates acommunication delay time of a signal transmitted from the gateway 222 tothe gateway 212 (step S104).

[0184] In response to receipt of the connection request from the gateway212, the gateway 222 makes a call to the facsimile machine 122, and thecalling/called communication delay estimating section 81 of the gateway222 estimates a communication delay time of a signal transmitted fromthe gateway 212 to the gateway 222 (step S105).

[0185] In response to receipt of the call from the gateway 222, thefacsimile machine 122 closes the line between the gateway 222 and thefacsimile machine 122 and transmits a CED signal, an NSF signal and aDIS in order.

[0186] At this time, a timer value change information transmittingsection 51 of the facsimile machine 122 transmits three kinds of timervalue change information, i.e. timer value change information of“twofold”, timer value change information of “threefold” and timer valuechange information of “fourfold”, to the gateway 222 as an NSF1-FGsignal (step S106).

[0187] The gateway 222 divides the NSF1-FG signal and the DIS receivedfrom the facsimile machine 122 into packets and transmits the packets tothe gateway 212.

[0188] At this time, the timer value change information detectingsection 82 of the gateway 222 detects the timer value changeinformation, i.e. the timer value change information of “twofold”, thetimer value change information of “threefold” and the timer value changeinformation of “fourfold”, included in the received NSF1 -FG signal.

[0189] Then, the receiver timer value change information selectingsection 83 of the gateway 222 selects, for example, the optimum timervalue change information of “twofold” from the detected timer valuechange information based on the communication delay time estimated atthe calling/called communication delay estimating section 81 (stepS107).

[0190] The gateway 212 reconstructs the NSF1-GG signal and the DIS fromthe packets received from the gateway 222 and transmits them to thefacsimile machine 112.

[0191] At this time, the timer value change information detectingsection 72 of the gateway 212 detects the timer value changeinformation, i.e. the timer value change information of “twofold”, thetimer value change information of “threefold” and the timer value changeinformation of “fourfold”, included in the received NSF1-GG signal.

[0192] Then, the transmitter timer value change information selectingsection 73 of the gateway 212 selects, for example, the optimum timervalue change information of “fourfold” from the detected timer valuechange information based on the communication delay time estimated atthe called/calling communication delay estimating section 71.

[0193] Based on the selection at the transmitter timer value changeinformation selecting section 73, the transmitter timer value changeinformation replacing section 74 replaces the timer value changeinformation of “twofold”, “threefold” and “fourfold” included in theNSF1-GG signal with the selected timer value change information of“fourfold”, and transmits an NSF2-GF signal including the substitutedtimer value change information of “fourfold” to the facsimile machine112 (step S108).

[0194] The facsimile machine 112 receives the NSF2-GF signal and theDIS. A timer value change information detecting section 63 of thecalling facsimile machine 112 detects the timer value change informationincluded in the NSF2-GF signal, that is, the timer value changeinformation of “fourfold” is detected. Accordingly, a timer value changeinformation selecting section 64 of the facsimile machine 112 selectsthe timer value change information of “fourfold”. Based on the selectionat the selecting section 64, a timer value changing section 53 increasesthe timer value fourfold. Simultaneously, a timer value changeinformation transmitting section 65 transmits an NSS1-FG signalincluding the timer value change information of “fourfold” to thegateway 212 (step S109).

[0195] Then, the facsimile machine transmits a TCF signal to the gateway212. Simultaneously, a timing monitor section 54 of the facsimilemachine 112 sets a fourfold-increased T4 timer value (12 seconds) in atimer 55 (step S110).

[0196] The gateway 212 divides the NSS1-FG signal received from thefacsimile machine 112 into packets and transmits the packets to thegateway 222 as an NSS1-GG signal, and then goes into a standby stateawaiting receipt of the TCF signal from the facsimile machine 112. Whenthe TCF signal is normally received, the gateway 212 goes into a standbystate awaiting receipt of a CFR signal from the called-side gateway 222(step S111).

[0197] The called-side gateway 222 reconstructs the NSS1-GG signal fromthe packets received from the calling-side gateway 212 and transmits anNSS2-GF signal to the called facsimile machine 122.

[0198] Specifically, as described before, the receiver timer valuechange information replacing section 84 of the gateway 222 replaces thetimer value change information of “fourfold” included in the receivedNSS1-GG signal with the timer value change information of “twofold”selected at the receiver timer value change information selectingsection 83 at step S107, and transmits the NSS2-GF signal including thesubstituted timer value change information of “twofold” to the calledfacsimile machine 122 (step S112).

[0199] Then, the gateway 222 produces a TCF signal according to a modemmode set by the NSS2-GF signal and transmits it to the facsimile machine122 (step S113).

[0200] When the NSS2-GF signal is received at the called facsimilemachine 122, a timer value change information detecting section 52thereof detects the timer value change information of “twofold” includedin the NSS2-GF signal. Then, a timer value changing section 53 of thefacsimile machine 122 increases the timer value twofold (step S114).

[0201] When the TCF signal is normally received from the gateway 222,the facsimile machine 122 transmits a CFR signal to the gateway 222.Simultaneously, at a timing monitor section 54 of the facsimile machine122, a twofold-increased T2 timer value (12 seconds) is set in a timer55 (step S115).

[0202] Since a subsequent portion of the sequence is like thecorresponding portion of the sequence of the first preferred embodimentshown in FIG. 7, explanation thereof is omitted.

[0203] As described above, in the calling facsimile machine 112, thetimer value is increased fourfold based on the timer value changeinformation of “fourfold” selected at the gateway 212. On the otherhand, in the called facsimile machine 122, the timer value is increasedtwofold based on the timer value change information of “twofold”selected at the gateway 222.

[0204] According to the foregoing second preferred embodiment of thepresent invention, the called/calling communication delay estimatingsection 71 of the calling-side gateway, for example, the gateway 212,estimates a communication delay time of a signal transmitted in adirection from the called-side gateway 222 to the calling-side gateway212.

[0205] The timer value change information detecting section 72 of thecalling-side gateway 212 detects the timer value change informationincluded in the NSF1-GG signal transmitted from the called-side gateway222. The transmitter timer value change information selecting section 73selects the optimum timer value change information with respect to thesignal transmission in the foregoing direction, from the detected timervalue change information based on the communication delay time estimatedat the called/calling communication delay estimating section 71.

[0206] The transmitter timer value change information replacing section74 replaces the timer value change information included in the receivedNSF1-GG signal with the timer value change information selected at thetransmitter timer value change information selecting section 73, andtransmits the NSF2-GF signal including the substituted timer valuechange information to the calling facsimile machine 112.

[0207] Accordingly, in the calling facsimile machine 112, the optimumtimer value change information with respect to the signal transmissionin the foregoing direction is selected based on the received NSF2-GFsignal.

[0208] On the other hand, the calling/called communication delayestimating section 81 of the called-side gateway 222 estimates acommunication delay time of a signal transmitted in a direction oppositeto the foregoing direction from the calling-side gateway 212 to thecalled-side gateway 222.

[0209] The timer value change information detecting section 82 of thecalled-side gateway 222 detects the timer value change informationincluded in the NSF1-FG signal transmitted from the called facsimilemachine 122. The receiver timer value change information selectingsection 83 selects the optimum timer value change information withrespect to the signal transmission in the foregoing opposite direction,from the detected timer value change information based on thecommunication delay time estimated at the calling/called communicationdelay estimating section 81.

[0210] The receiver timer value change information replacing section 84replaces the timer value change information included in the NSS1-GGsignal received from the gateway 212 with the timer value changeinformation selected at the receiver timer value change informationselecting section 83, and transmits the NSS2-GF signal including thesubstituted timer value change information to the called facsimilemachine 122.

[0211] Accordingly, in the called facsimile machine 122, the optimumtimer value change information with respect to the signal transmissionin the foregoing opposite direction is selected based on the receivedNSS2-GF signal.

[0212] Thus, in the second preferred embodiment of the presentinvention, a communication delay time of a signal transmitted from thegateway 222 to the gateway 212 can be estimated by the gateway 212 tochange a timer value of the facsimile machine 112 using timer valuechange information selected based on the estimated signal delay.

[0213] Similarly, a communication delay time of a signal transmittedfrom the gateway 212 to the gateway 222 can be estimated by the gateway222 to change a timer value of the facsimile machine 122 using timervalue change information selected based on the estimated signal delay.

[0214] In the foregoing first preferred embodiment, the timer valuechange information is commonly selected at the calling and calledfacsimile machines irrespective of the state of the packet communicationnetwork 400.

[0215] On the other hand, in the second preferred embodiment, theoptimum timer value change information can be selected for each of thecalling and called facsimile machines in consideration of the state ofthe packet communication network 400 so that the optimum timer valuescan be set in both facsimile machines. This can achieve more reliablefacsimile communication.

[0216] At step S108 in FIG. 11, the transmitter timer value changeinformation selecting section 73 of the gateway 212 selects only onekind of the optimum timer value change information, i.e. the timer valuechange information of “fourfold”, from the timer value changeinformation of “twofold”, “threefold” and “fourfold” included in theNSF1-GG signal. However, it may be arranged that the transmitter timervalue change information selecting section 73 selects more than one kindof the optimum timer value change information. In this case, the callingfacsimile machine 112 is arranged to select one from the plural kinds ofthe optimum timer value change information.

[0217] In the first and second preferred embodiments, the timer valuechange information is composed of information for increasing the timervalue by integer times, such as “twofold, “threefold” and “fourfold”.However, it may be arranged that timer value change information iscomposed of information for increasing the timer value by addition, orthat timer value change information is in the form of changed timervalues themselves. In other words, it is sufficient that timer valuechange information is composed of information which can change the timervalue easily and precisely.

[0218] <Third Embodiment>

[0219]FIG. 12 is a diagram showing a structure of a facsimilecommunication system according to the third preferred embodiment of thepresent invention.

[0220] As shown in FIG. 12, a facsimile machine 113 is connected to agateway 213 via a telephone line 310. The gateway 213 is connected to apacket communication network 400. On the other hand, a facsimile machine123 is connected to a gateway 223 via a telephone line 320. The gateway223 is connected to the packet communication network 400.

[0221] Facsimile communication between the facsimile machine 113 and thefacsimile machine 123 is carried out via the packet communicationnetwork 400.

[0222] The facsimile machines 113 and 123 have mutually the samestructure, and the gateways 213 and 223 also have mutually the samestructure. Accordingly, the facsimile machine 113 and the gateway 213will be described hereinbelow.

[0223] The facsimile machine 113 is the same in hardware structure asthe facsimile machine 111 shown in FIG. 4, but a ROM 13 of the facsimilemachine 113 stores, instead of the program for producing the functionalblocks shown in FIGS. 1 and 2, a flow control program which is executedbetween the facsimile machine 113 and the gateway 213.

[0224]FIG. 13 shows functional blocks of the facsimile machine 113produced by executing the flow control program stored in the ROM 13. Asappreciated, the dial number storage section 61 and the dial numbersearch section 62 shown in FIG. 2 are not produced in the facsimilemachine 113.

[0225] In FIG. 13, a re-setting command signal receiving section 91 hasa function of detecting a response signal from the gateway 213 relativeto signal transmission from the facsimile machine 113 to the gateway213, and a further function of detecting a RNR (Receive Not Ready)signal from the gateway 213.

[0226] A timing monitor section 54 has a function of monitoring whethera signal from a counterpart facsimile machine (facsimile machine 123) isreceived within a normal response time. Specifically, the timing monitorsection 54 sets a timer value of the ITU-T Recommendation T. 30 in atimer 55 and, when a response signal from the gateway 213 is notreceived within a time represented the timer value set in the timer 55,the timer monitor section 54 outputs a time-out signal TOUT indicativeof it to the gateway 213.

[0227] The timing monitor section 54 has a further function of, when there-setting command signal receiving section 91 detects an RNR signalfrom the gateway 213, interrupting counting of the timer 55 and settingagain the same timer value in the timer 55, i.e. re-setting the timer 55to the same timer value.

[0228] The re-setting response signal transmitting section 92 has afunction of transmitting an RR (Receive Ready) signal to the gateway 213when the timer 55 is re-set to the same timer value in response to theRNR signal detected at the re-setting command signal receiving section91.

[0229] The gateway 213 is the same in hardware structure as the gateway211 shown in FIG. 5, but a ROM 33 thereof stores a flow control programwhich is executed between the gateway 213 and the facsimile machine 113.

[0230]FIG. 14 shows functional blocks of the gateway 213 produced byexecuting the flow control program stored in the ROM 33.

[0231] In FIG. 14, a timing monitor section 93 monitors whether aresponse signal from the facsimile machine 123 via the gateway 223 isreceived within a normal response time, after transmitting a signalreceived from the facsimile machine 113 to the facsimile machine 123 viathe gateway 223.

[0232] Specifically, the timing monitor section 93 sets a timer value ina timer 94 and, when the response signal via the gateway 223 is notreceived within a time represented by the timer value set in the timer94, the timer monitor section 93 outputs a time-out signal TOUTindicative of it to a re-setting command signal transmitting section 95.

[0233] The timer value of the timer 94 is set corresponding to the timervalue of the timer 55 of the facsimile machine 113. The timer value ofthe timer 94 is set to be smaller than the timer value of the timer 55of the facsimile machine 113 in consideration of a time in which asignal transmitted from the facsimile machine 113 is received at thegateway 213 and a time in which a signal transmitted from the gateway213 is received at the facsimile machine 113.

[0234] In response to receipt of the time-out signal TOUT from thetiming monitor section 93, the re-setting command signal transmittingsection 95 transmits an RNR signal to the facsimile machine 113.

[0235] When the facsimile machine 113 transmits an RR signal in responseto the RNR signal transmitted from the re-setting command signaltransmitting section 95 to the facsimile machine 113, a re-settingresponse signal receiving section 96 detects the RR signal.

[0236] The timing monitor section 93 has a further function of, when there-setting response signal receiving section 96 detects the RR signalfrom the facsimile machine 113, interrupting counting of the timer 94and re-setting the timer 94 to the same timer value.

[0237] Until a response signal from the facsimile machine 123 via thegateway 223 is received within a time represented by a timer value setin the timer 94, the timing monitor section 93 repeats re-setting of thetimer 94.

[0238]FIG. 15 is a diagram showing a facsimile communication operationsequence according to the third preferred embodiment of the presentinvention.

[0239] It is assumed that the facsimile machine 113 is a callingfacsimile machine working as a transmitter for transmitting image data,while the facsimile machine 123 is a called facsimile machine working asa receiver for receiving image data.

[0240] First, the facsimile machine 113 makes a call to the gateway 213(step S201). In response to the call from the facsimile machine 113 tothe gateway 213, the line is established therebetween. Then, a dial toneDT is transmitted from the gateway 213 to the facsimile machine 113(step S202). In response to receipt of the dial tone DT from the gateway213, the facsimile machine 113 transmits a dial number (PB signal) ofthe facsimile machine 123 to the gateway 213 (step S203).

[0241] In response to receipt of the PB signal, the gateway 213retrieves an IP address of the called-side gateway 223 in the packetcommunication network 400 from addresses stored in a RAM 34 of thecalling-side gateway 213, and transmits to the called-side gateway 223 aconnection request adding the dial number of the facsimile machine 123(step S204).

[0242] In response to receipt of the connection request from the gateway213, the gateway 223 makes a call to the facsimile machine 123 (stepS205).

[0243] In response to receipt of the call from the gateway 223, thefacsimile machine 123 closes the line between the gateway 223 and thefacsimile machine 123 and transmits a CED signal, an NSF signal and aDIS in order to the gateway 223. The NSF signal includes flow controlinformation indicative of having a flow control function (step S206).

[0244] The gateway 223 divides the NSF signal and the DIS received fromthe facsimile machine 123 into packets and transmits the packets to thegateway 213 (step S207).

[0245] The gateway 213 reconstructs the NSF signal and the DIS from thepackets received from the gateway 223 and transmits them to thefacsimile machine 113 (step S208).

[0246] When the NSF signal and the DIS are received, the facsimilemachine 113 detects the flow control information included in the NSFsignal so that execution of a flow control is set in the facsimilemachine 113. Then, the facsimile machine 113 transmits to the gateway213 an NSS signal including flow control information indicative of thesetting of flow control execution (step S209).

[0247] Subsequently, the facsimile machine 113 transmits a TCF signal tothe gateway 213. Simultaneously, the timing monitor section 54 of thefacsimile machine 113 sets a T4 timer value (for example, 3 seconds) inthe timer 55 (step S210).

[0248] The calling-side gateway 213 divides the NSS signal received fromthe facsimile machine 113 into packets and transmits the packets to thecalled-side gateway 223, and then goes into a standby state awaitingreceipt of the TCF signal from the facsimile machine 113. In themeantime, the gateway 213 detects the flow control information includedin the received NSS signal so that flow control execution is set in thegateway 213. Thereafter, when the TCF signal is normally received fromthe calling facsimile machine 113, the calling-side gateway 213 goesinto a standby state awaiting receipt of a CFR signal from thecalled-side gateway 223. At this time, the timing monitor section 93 ofthe gateway 213 sets a T4a timer value (for example, 2 seconds) in thetimer 94 (step S211).

[0249] The called-side gateway 223 reconstructs the NSS signal from thepackets received from the calling-side gateway 213 and transmits the NSSsignal to the called facsimile machine 123. In the meantime, the gateway223 detects the flow control information included in the received NSSsignal so that flow control execution is set in the gateway 223 (stepS212).

[0250] Then, the gateway 223 produces a TCF signal according to a modemmode set by the NSS signal and transmits it to the called facsimilemachine 123 (step S213).

[0251] When the NSS signal is received, the facsimile machine 123detects the flow control information included in the NSS signal so thatflow control execution is set in the facsimile machine 123 (step S214).

[0252] After receipt of the NSS signal, when the TCF signal is normallyreceived from the gateway 223, the facsimile machine 123 transmits a CFRsignal to the gateway 223. Simultaneously, the timing monitor section 54of the facsimile machine 123 sets a T2 timer value (for example, 6seconds) in the timer 55 (step S215).

[0253] When the CFR signal is received from the facsimile machine 123,the gateway 223 divides the received CFR signal into packets andtransmits the packets to the gateway 213. Simultaneously, the timingmonitor section 93 of the gateway 223 set a T2a timer value (forexample, 5 seconds) in the timer 94. At this time, if a largecommunication delay occurs in the packet communication network 400, thepackets (CFR signal) reach the gateway 213 with a corresponding delay(step S216).

[0254] If, due to this delay, the gateway 213 can not receive thepackets (CFR signal) from the gateway 223 within the T4a timer value (2seconds) set in the timer 94 at step S211, the re-setting command signaltransmitting section 95 of the gateway 213 transmits an RNR signal tothe facsimile machine 113 after a lapse of the T4a timer value from thereceipt of the TCF signal from the facsimile machine 113 (step S217).

[0255] When the RNR signal from the gateway 213 is received, there-setting command signal receiving section 91 of the facsimile machine113 detects it. In response to the detection of the RNR signal, thetiming monitor section 54 of the facsimile machine 113 re-sets the timer55 to the same T4 timer value (3 seconds), and the re-setting responsesignal transmitting section 92 transmits an RR signal to the gateway213.

[0256] When the RR signal from the facsimile machine 113 is received atthe re-setting response signal receiving section 96 of the gateway 213,the timing monitor section 93 re-sets the timer 94 to the same T4a timervalue (2 seconds) (step S218).

[0257] Further, if the gateway 213 can not receive the packets (CFRsignal) from the gateway 223 within the T4a timer value (2 seconds)re-set in the timer 94 at step S218, the resetting command signaltransmitting section 95 of the gateway 213 retransmits the RNR signal tothe facsimile machine 113 after a lapse of the T4a timer value re-set inthe timer 94 (step S219).

[0258] When the re-setting command signal receiving section 91 of thefacsimile machine 113 detects the retransmitted RNR signal, the timingmonitor section 54 re-sets the timer 55 to the same T4 timer value (3seconds). Then, the re-setting response signal transmitting section 92retransmits the RR signal to the gateway 213.

[0259] When the re-setting response signal receiving section 96 of thegateway 213 receives the RR signal retransmitted from the facsimilemachine 113, the timing monitor section 93 re-sets the timer 94 to thesame T4a timer value (2 seconds) (step S220).

[0260] As described above, until the gateway 213 receives the CFR signalfrom the gateway 223, the RNR and RR signals are exchanged between thegateway 213 and the facsimile machine 113 so that the timer 94 and thetimer 55 are re-set to the given timer values, respectively. With thisarrangement, the delay of the CFR signal transmitted from the gateway223 to the gateway 213 can be absorbed. If, however, the CFR signal isnot received at the gateway 213 even after given number times exchangesof the RNR and RR signals, it is judged that a communication failure hasoccurred so that the communication is forcibly interrupted.

[0261] When the packets (CFR signal) are received from the gateway 223,the gateway 213 reconstructs the CFR signal from the received packetsand transmits it to the facsimile machine 113 (step S221).

[0262] In response to receipt of the CFR signal from the gateway 213,the facsimile machine 113 transmits image data to the gateway 213 (stepS222).

[0263] The gateway 213 divides the image data received from thefacsimile machine 113 into packets and transmits the packets to thegateway 223. At this time, if a large communication delay is caused inthe packet communication network 400, the packets (image data) reach thegateway 223 with a corresponding delay (step S223).

[0264] If, due to this delay, the packets (image data) are not receivedat the gateway 223 within the T2a timer value (5 seconds) set in thetimer 94 of the gateway 223 at step S216, the re-setting command signaltransmitting section 95 of the gateway 223 transmits an RNR signal tothe facsimile machine 123 (step S224).

[0265] When the RNR signal from the gateway 223 is received, there-setting command signal receiving section 91 of the facsimile machine123 detects it. In response to the detection of the RNR signal, thetiming monitor section 54 of the facsimile machine 123 re-sets the timer55 to the same T2 timer value (6 seconds), and the re-setting responsesignal transmitting section 92 transmits an RR signal to the gateway223.

[0266] When the RR signal from the facsimile machine 123 is received atthe re-setting response signal receiving section 96 of the gateway 223,the timing monitor section 93 re-sets the timer 94 to the same T2a timervalue (5 seconds) (step S225).

[0267] In this fashion, until the gateway 223 receives the packets(image data) from the gateway 213, the RNR and RR signals are exchangedbetween the gateway 223 and the facsimile machine 123 so that the timer94 and the timer 55 are re-set to the given timer values, respectively.With this arrangement, the delay of the image data transmitted from thegateway 213 to the gateway 223 can be absorbed. If, however, the imagedata are not received at the gateway 223 even after given number timesexchanges of the RNR and RR signals, it is judged that a communicationfailure has occurred so that the communication is forcibly interrupted.

[0268] When the packets (image data) are received from the gateway 213,the gateway 223 reconstructs the image data from the received packetsand transmits the image data to the facsimile machine 123. Then, theimage data is received at the facsimile machine 123 (step S226).

[0269] After the transmission of the image data is finished, the callingfacsimile machine 113 transmits an EOP signal to the gateway 213.Simultaneously, the timing monitor section 54 of the facsimile machine113 sets a T4 timer value (for example, 3 seconds) in the timer 55 (stepS227).

[0270] The gateway 213 divides the received EOP signal into packets andtransmits the packets to the gateway 223. At this time, the timingmonitor section 93 of the gateway 213 sets a T4a timer value (forexample, 2 seconds) in the timer 94. If the delay occurs in transmissionof the image data to the gateway 223 as described at step S223, a delayalso occurs in transmission of the EOP signal to the gateway 223 (stepS228).

[0271] The gateway 223 reconstructs the EOP signal from the packetsreceived from the gateway 213 and transmits the EOP signal to thefacsimile machine 123 (step S229).

[0272] In response to receipt of the EOP signal from the gateway 223,the facsimile machine 123 transmits an MCF signal to the gateway 223(step S230).

[0273] The gateway 223 divides the received MCF signal into packets andtransmits the packets to the gateway 213.

[0274] If the delay occurs in transmission of the image data to thegateway 223 as described at step S223, a delay also occurs intransmission of the MCF signal from the gateway 223 to the gateway 213.

[0275] Thus, the MCF signal reaches the gateway 213 while beingsubjected to an influence of the delay of the image data at step S223(step S231).

[0276] In this case, if the gateway 213 does not receive the packets(MCF signal) from the gateway 223 within the T4a timer value (2 seconds)set in the timer 94 at step S228, the resetting command signaltransmitting section 95 of the gateway 213 transmits an RNR signal tothe facsimile machine 113 (step S232).

[0277] When the RNR signal from the gateway 213 is received, there-setting command signal receiving section 91 of the facsimile machine113 detects it. In response to the detection of the RNR signal, thetiming monitor section 54 of the facsimile machine 113 re-sets the timer55 to the same T4 timer value (3 seconds), and the re-setting responsesignal transmitting section 92 transmits an RR signal to the gateway213.

[0278] When the RR signal from the facsimile machine 113 is received atthe re-setting response signal receiving section 96 of the gateway 213,the timing monitor section 93 re-sets the timer 94 to the same T4a timervalue (2 seconds) (step S233).

[0279] Further, if the gateway 213 does not receive the packets (MCFsignal) from the gateway 223 within the T4a timer value (2 seconds)re-set in the timer 94 at step S233, the resetting command signaltransmitting section 95 of the gateway 213 retransmits the RNR signal tothe facsimile machine 113 (step S234).

[0280] When the re-setting command signal receiving section 91 of thefacsimile machine 113 detects the retransmitted RNR signal, the timingmonitor section 54 re-sets the timer 55 to the same T4 timer value (3seconds). Then, the re-setting response signal transmitting section 92retransmits the RR signal to the gateway 213 (step S235).

[0281] As described above, until the gateway 213 receives the MCF signalfrom the gateway 223, the RNR and RR signals are exchanged between thegateway 213 and the facsimile machine 113 so that the timer 94 and thetimer 55 are re-set to the given timer values, respectively. With thisarrangement, the delay of the MCF signal transmitted from the gateway223 to the gateway 213 can be absorbed. If, however, the MCF signal isnot received at the gateway 213 even after given number times exchangesof the RNR and RR signals, it is judged that a communication failure hasoccurred so that the communication is forcibly interrupted.

[0282] When the packets (MCF signal) are received from the gateway 223,the gateway 213 reconstructs the MCF signal from the received packetsand transmits it to the facsimile machine 113 (step S236).

[0283] In response to receipt of the MCF signal, the facsimile machine113 transmits a DCN signal to the gateway 213 so that the line betweenthe facsimile machine 113 and the gateway 213 is disconnected (stepS237).

[0284] The DCN signal is transmitted to the facsimile machine 123 viathe gateways 213 and 223 to finally disconnect the line between thefacsimile machine 123 and the gateway 223, so that the communicationbetween the facsimile machines 113 and 123 is terminated (step S238).

[0285] As described above, according to the third preferred embodimentof the present invention, when transmission, from the gateway 213 to thegateway 223, of a response signal relative to a transmitted signal (e.g.image data in response to CFR signal) is delayed, until the gateway 223receives the response signal from the gateway 213, the RNR and RRsignals are exchanged between the gateway 223 and the facsimile machine123 so that the timer 94 and the timer 55 are re-set to the given timervalues, respectively. With this arrangement, the delay of the signal canbe absorbed.

[0286] Similarly, when transmission, from the gateway 223 to the gateway213, of a response signal relative to a transmitted signal (e.g. CFRsignal in response to TCF signal; MCF signal in response to EOP signal)is delayed, until the gateway 213 receives the response signal from thegateway 223, the RNR and RR signals are exchanged between the gateway213 and the facsimile machine 113 so that the timer 94 and the timer 55are re-set to the given timer values, respectively. With thisarrangement, the delay of the signal can be absorbed.

[0287] Therefore, since the communication delay between the gateway 213and the gateway 223 can be absorbed, the highly reliable facsimilecommunication can be realized.

[0288] In the foregoing first and second preferred embodiments, thecommunication delay between the gateways is absorbed by the changedtimer values. However, when the state of the packet communicationnetwork 400 changes momentarily, a time loss becomes large. For example,when the timer value is increased twofold, a time for judging whetherretransmission is necessary or not is also increased twofold.

[0289] On the other hand, in the third preferred embodiment, the RNR andRR signals are exchanged between the gateway and the facsimile machineonly when the signal is delayed, thereby to absorb the delay of thesignal. Thus, the delay of the signal can be absorbed more efficiently.

[0290] In the third preferred embodiment, the flow controls are executedat both sides, i.e. between the gateway 213 and the facsimile machine113 and between the gateway 223 and the facsimile machine 123. However,even if it is arranged to execute the flow control only at one side, thedelay of the signal from the other side can be absorbed.

[0291] In the foregoing first to third preferred embodiments, thefacsimile machines are connected to the gateways via the telephonenetwork and the gateways are connected to the packet communicationnetwork, so as to constitute the facsimile communication system.However, the packet communication network may be replaced with anothercommunication network, such as a radio communication network. Thepresent invention is effectively applicable to facsimile communicationimplemented via a communication network whose communication delay isgreater than that of the telephone network (wired).

[0292] Further, the present invention is also applicable to a facsimilecommunication system wherein a facsimile machine is provided with a LANinterface and an LCU (see FIG. 5) so as to constitute a compositefacsimile machine and the composite facsimile machine is connected tothe packet communication network.

[0293] <Fourth Embodiment>

[0294]FIG. 16 is a diagram showing a structure of a facsimilecommunication system according to the fourth preferred embodiment of thepresent invention.

[0295] As shown in FIG. 16, a facsimile machine 114 and a facsimilemachine 124 are directly connected to a packet communication network400. Facsimile communication between the facsimile machine 114 and thefacsimile machine 124 is carried out via the packet communicationnetwork 400. Since the facsimile machines 114 and 124 have mutually thesame structure, the facsimile machine 114 will be described hereinbelow.

[0296]FIG. 17 is a block diagram showing a hardware structure of thefacsimile machine 114 according to the fourth preferred embodiment ofthe present invention. As shown in FIG. 17, the facsimile machine 114 isbasically the same in hardware structure as the facsimile machine 111shown in FIG. 4, except that a LAN interface 43 and an LCU 44 areprovided instead of the modem NCU interface 15, the modem 16 and the NCU17.

[0297] The LAN interface 43 is connected to a bus 11 and the LCU 44. TheLAN interface 43 divides a control signal or image data into packetsbefore sending it out to the packet communication network 400 andreconstructs a control signal or image data from packets received viathe packet communication network 400. The LCU 44 is connected to the LANinterface 43 and the packet communication network 400 and controlsconnection and disconnection relative to a counterpart facsimilemachine.

[0298] When transmitting image data, the image data stored in a RAM 14is transferred to the LAN interface 43 via the bus 11. The image datatransferred to the LAN interface 43 is divided into packets at the LANinterface 43 and sent out to the packet communication network 400 viathe LCU 44. On the other hand, when packets (image data) are received atthe LCU 44 via the packet communication network 400, the LAN interface43 reconstructs image data from the received packets. The reconstructedimage data is stored in the RAM 14 via the bus 11.

[0299] When transmitting a control signal, the control signal is readout from a ROM 13 by a CPU 12 and transferred to the LAN interface 43via the bus 11. The control signal transferred to the LAN interface 43is divided into packets at the LAN interface 43 and sent out to thepacket communication network 400 via the LCU 44. On the other hand, whenpackets (control signal) are received at the LCU 44 via the packetcommunication network 400, the LAN interface 43 reconstructs a controlsignal from the received packets. The reconstructed control signal istransferred to the CPU 12 via the bus 11. The CPU 12 analyzes thecontrol signal and implements a communication procedure according to theanalyzed contents.

[0300] In FIG. 17, the RAM 14 stores a table including dial numbers ofcounterpart facsimile machines and IP addresses thereof in the packetcommunication network such that the dial number and the IP address aremutually retrievable from each other. When a dial number of acounterpart facsimile machine is inputted via an operation displaysection 28, an IP address corresponding to the inputted dial number isread out from the table to make a connection request via the LCU 44.

[0301] Further, in FIG. 17, the ROM 13 stores a timer value changecontrol program for changing a timer value of the facsimile machine 114directly connected to the packet communication network 400. By executingthe timer value change control program, functional blocks shown in FIGS.1 and 2 are produced like in the foregoing first preferred embodiment.However, the fourth preferred embodiment differs from the firstpreferred embodiment in timer value change information and timer valueselecting method.

[0302] Specifically, in this embodiment, when the facsimile machine 114works as a called facsimile machine, a timer value change informationtransmitting section 51 of FIG. 1 transmits timer value changeinformation indicative of whether the facsimile machine 114 is directlyconnected to the packet communication network 400 and whether thefacsimile machine 114 can be operated based on a timer value designatedby a calling facsimile machine. A timer value change informationdetecting section 52 detects timer value change information receivedfrom the calling facsimile machine and sends it to a timer valuechanging section 53. The timer value changing section 53 changes a timervalue based on the detected timer value change information and outputs achanged timer value to a timing monitor section 54. The timing monitorsection 54 sets the changed timer value in a timer 55.

[0303] On the other hand, when the facsimile machine 114 works as acalling facsimile machine, a timer value change information detectingsection 63 of FIG. 2 detects timer value change information receivedfrom a called facsimile machine and sends it to a timer value changeinformation selecting section 64. Knowing that the called facsimilemachine is directly connected to the packet communication network andcan be operated by a timer value designated by the subject facsimilemachine (calling facsimile machine), the timer value change informationselecting section 64 selects a Tmax value which represents a maximumtime in which one communication should be implemented. The Tmax value isselected depending on a frequency band acquired in the packetcommunication network 400, a time required from transmission of aconnection request to receipt of an NSF signal, and an image data amountto be transmitted. The timer value changing section 53 changes a timervalue to the Tmax value selected at the timer value change informationselecting section 64 and outputs it to a timing monitor section 54 and atimer value change information transmitting section 65. The timingmonitor section 54 sets the received Tmax value in a timer 55, while thetransmitting section 65 transmits to the called facsimile machine timervalue change information representing that the calling facsimile machine114 is directly connected to the packet communication network 400 andimplements one communication within the Tmax value.

[0304] Now, an operation of the facsimile communication system shown inFIG. 16 will be described with reference to FIG. 18.

[0305] In an example shown in FIG. 18, when a calling facsimile machine,such as the facsimile machine 114, is inputted, via an operation displaysection 28, with a dial number of the facsimile machine 124 to be acalled facsimile machine, the CPU 12 of the facsimile machine 114retrieves a corresponding IP address from the foregoing table (dialnumber storage section 61 shown in FIG. 2) stored in the RAM 14 andtransmits a connection request to the called facsimile machine 124 (stepS301). In response to receipt of the connection request from the callingfacsimile machine 114, the called facsimile machine 124 transmits an NSFsignal and a DIS to the calling facsimile machine 114. The NSF signalincludes a signal notifying that the called facsimile machine 124 isdirectly connected to the packet communication network 400 and can beoperated based on a timer value designated by the calling facsimilemachine 114 (step S302).

[0306] In response to the NSF signal, the calling facsimile machine 114transmits an NSS signal to the called facsimile machine 124. The NSSsignal includes a signal notifying that the calling facsimile machine114 is also directly connected to the packet communication network 400and thus is free of the limitation of the timer values regulated by theITU-T Recommendation T. 30 and that one communication is implementedwithin a time defined by the Tmax value (step S303). The Tmax value,i.e. a timer value for one communication, is determined based on afrequency band of the communication acquired in the packet communicationnetwork 400, a delay caused from transmission of the connection requestto receipt of the NSF signal, and an image data amount to betransmitted.

[0307] The called facsimile machine 124 knows from the NSS signal thatthe communication is free of the timer limitation of the ITU-TRecommendation T. 30, and sets in the timer 55 of the timing monitorsection 54 the Tmax timer value notified from the calling facsimilemachine 114, and then transmits a CFR signal to the calling facsimilemachine 114 (step S304).

[0308] In response to receipt of the CFR signal, the calling facsimilemachine 114 transmits image data per packet to the called facsimilemachine 124 (step S305). When the image data per packet is received, thecalled facsimile machine 124 transmits an ACK signal to the callingfacsimile machine 114 (step S306).

[0309] In the example of FIG. 18, the calling facsimile machine 114transmits image data 1 to image data 8 per packet (steps S305, S307, . .. , S319) and the called facsimile machine 124 transmits ACK signals inresponse to receipt of the corresponding packets (steps S306, S308, . .. , S320). Transmission of the image data 1 to the image data 8 is freeof the limitation of the timer values regulated by the ITU-TRecommendation T. 30. Accordingly, even if a delay is caused intransmission of each of the image data 1 to 8, the communication is notinterrupted until a lapse of the Tmax value.

[0310] After the transmission of the image data 1 to 8, the callingfacsimile machine 114 transmits an EOP signal to the called facsimilemachine 124 (step S321). In response to receipt of the EOP signal, thecalled facsimile machine 124 transmits an MCF signal to the callingfacsimile machine 114 (step S322). The calling facsimile machine 114recognizes from receipt of the MCF signal that the transmission of theimage data is normally carried out, and transmits a DCN signal to thecalled facsimile machine 124 so that the communication is finished (stepS323).

[0311] As described above, according to the fourth preferred embodimentof the present invention, the calling facsimile machine determines themaximum time for implementing one communication based on a frequencyband of the communication acquired in the packet communication network,a time required from transmission of the connection request to receiptof the NSF signal, and the image data amount to be transmitted, andtransmits the determined maximum time to the called facsimile machine asa timer value. Since the communication between the calling and calledfacsimile machines is executed by monitoring the timer value of theforegoing maximum time, even if a communication delay is temporarilycaused in the packet communication network, the highly reliablecommunication can be achieved.

[0312] In the foregoing first to third preferred embodiments, the timervalue change information or the flow control information is transmittedusing the NSF signal and the NSS signal regulated by the ITU-TRecommendation T. 30. However, if such information is adopted as thestandard communication capability information of the ITU-TRecommendation T. 30, it can be transmitted using the DIS and the DCS.

[0313] While the present invention has been described in terms of thepreferred embodiments, the invention is not to be limited thereto, butcan be embodied in various ways without departing from the principle ofthe invention as defined in the appended claims.

I/we claim:
 1. A facsimile machine communicating with a counterpartfacsimile machine through a gateway, comprising: a timing monitorsection which sets an appointed timer value into a timer and monitorswhether said facsimile machine received a response signal from saidcounterpart facsimile machine within said timer value; and a signalreceiving section which receives a prescribed signal from said gatewayand instructs said timing monitor section to re-set said timer valueinto said timer when said prescribed signal is received before the timeindicated by said timer value passed.
 2. The facsimile machine accordingto claim 1, wherein said prescribed signal is receive not ready (RNR)signal. 3 The facsimile machine according to claim 1, moreovercomprising: a reply signal transmitting section which transmits aprescribed response signal to said gateway with said timer value isre-set.
 4. The facsimile machine according to claim 3, wherein saidprescribed reply signal is receive ready (RR) signal.
 5. A method ofconducting facsimile communication between a facsimile machine and acounterpart facsimile machine through a gateway, comprising the stepsof: setting an appointed timer value into a timer of said facsimilemachine; monitoring whether said facsimile machine received a responsesignal from said counterpart facsimile machine within the time indicatedby said timer value; re-setting said timer value into said timer whensaid facsimile machine received a prescribed signal from said gatewaybefore the time indicated by said timer value passed; and re-monitoringwhether said response signal is received.
 6. The method of conductingfacsimile communication according to claim 5, wherein said prescribedsignal is receive not ready (RNR) signal.
 7. The method of conductingfacsimile communication according to claim 5, moreover comprising thestep of: transmitting a prescribed reply signal to said gateway by saidfacsimile machine with said timer value is re-set.
 8. The method ofconducting facsimile communication according to claim 7, wherein saidprescribed reply signal is receive ready (RR) signal.